Anti-icing of variable pitch propeller blades



May 15, 1951 J. s'ruARTJjl,

ANTI-ICING 0F VARIABLE PITCH PROPELLER BLADES Filed May 1, 1944 ET AL z Sheets-Sheet 1 a. L r WRMMH ZZ 35 R w w m N5; T PE ER w Jww 1951 J. STUART, n1 ETYAL 2, 53,218

ANTI-ICING OF VARIABLE PITCH PROPELLER BLADES Filed May 1, 1944 v 3 Sheets-Sheet 2 MAN/FOLD Alf? PUMP "i.

/ A INVENTOR q; WHRRE/VZZEEHKLE Y ATTORN EYS Patented May I5, 1951 UNITED STATES ATENT OFFICE ANTI-ICING OF VARIABLE PITCH PROPELLER BLADES V! are Application May 1, 1944, Serial No. 533,562

8 Claims. 1

This invention relates to pitch shiftable propellers for aircraft and means for inhibiting and removing the formation of ice thereon.

One of the principle objects of the invention is to prevent the formation of ice on the surfaces of airfoils particularly of propeller constructions.

Another object of the invention is to provide means for inhibiting the formation of ice on propeller blades and for removing ice so formed without interfering with the propeller rotation, or pitch shifting of the blades.

Another object of the invention is to provide a hot air heating system for blades of the hollow spar type without structural weakness of the blade or deterioration due to corrosive effects.

Another object of the invention is to provide means for conducting heated air from a heat transfer unit to the interior of a hollow blade of the pitch shiftable variety, without interfering with the freedom of blade movement.

Another object of the invention is to force clean hot air under pressure from a heat exchange unit throughout the length of a pitch shiftable rotating propeller blade to be ejected at the tip in prohibiting ice formation on the blade or for removing ice that has formed thereon.

A still further object is to provide a hollow propeller blade of the pitch shiftable class that is subject to hot air heating for ice inhibition or removal.

Yet another object is to provide suitable balance means for blades subject to hot air heating.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Fig. 1 is a view in elevation with parts broken away to show details in section, for a hot air heating system of ice inhibiting and removing means.

Fig. 2 is a front elevational view of the same.

Fig. 3 is an enlarged fragmentary sectional view substantially as indicated by the line and arrows 33 of Fig. 2.

Fig. 4 is a schematic view of the blade heating system.

Fig. 5 is a sectional view through the tip of the blade such as indicated by the line and arrows 55 of Fig. 4 and Fig. 6.

Fig. 6 is a plan view of a propeller blade illustrating the means for conducting the heated air throughout its length.

Fig. '7 is a transverse sectional view through the base end of the blade substantially as indicated by the line and arrows 1-1 of Figs. 1, 6 and 8.

Fig. 8 is a chordwise section of the blade and root portion substantially as indicated by the line and arrows $8' of Fig. 7, and showing details of hot air conduit entry and the distribution of balance means.

Fig. 9 is a transverse section at right angles thereto substantially as indicated by the line and arrows 99 of Fig. '7.

With particular reference to the drawings, It refers to a propeller hub having sockets l2 rotatably mounting blades I4 for pitch shifting movement by means of shanks l6 journalled for rotation on their axes in the sockets l2, which hub is enclosed by a spinner is secured at its base end to a bulkhead 29 extending radially outward from a regulator housing 22 and piloted at the nose end by an adapter sleeve 25!- fastened to the forward end of the hub Ill. The blades :4 are of hollow construction insofar as the shank I6 is formed of a tapered tube serving as a spar 26 extending substantially the length of the blade, and has encompassing it a sheath of sheet metal folded to form an integrally joined pair of face members such as a pressure face 28 and a camber face 35 joined by a folded leading edge 32 and a lapped bonded trailing edge 34. The tip end of the blade is closed at 36 by a continuation of the lapped bonded edge except for a small aperture 38 providing a condensation vent and an aperture or rearwardly directed slit 40 providing a hot air exit. It is most desirable that the aperture 38 be located at the most radially remote part of the tip so that there will. be no pocket for the lodgement of moisture, and so that any condensate forming in the hollow spaces 132, M of the blade may easily drain out of the aperture 38, at least in response to centrifugal force. The aperture or slit 4!! is desirably located near the tip of the blade but somewhat near the trailing edge 34 of the blade. By so locating the aperture M, advantage is taken of the jet propulsive effect that at least partially compensates for the energy expended in placing the air of the heating system under pressure. Where the blade centrifugal pumping action, plus the head due to propeller slip stream and/or aircraft motion is not effective for blades in the feathered position, a pump in the system will be incorporated. Where the air flow through the port 56 is markedly in excess of that required for de-icing, the exhausted air will partially or entirely drive the propeller by the reaction of the jet effect. The end of the spar 26 is closed off by any means, such as by pinching together and/or bonding as at M, such that the apertures 38 and M! offer exit for the hollow chambers 52, 44 on either side of the spar and inside of the face members.

Heated air under suitable pressure is conducted to the base end of the blade by a conduit 48 projecting through the blade bulkhead 59 and emptying into the hollow space 42 on the leading edge side of the spar 25, there being a gasket 52 and a clamp washer :3 carried by the bulkhead to seal the connection and flex close to the conduit as it waves due to pitch shifting of the blade. The radially inward end of the chamber 44 is completely closed off by a bulkhead 56 as will presently be described. The con duit 48 is flared at 53 and secured to a ring 60 whose periphery is curved to closely lit the bore of an ell 62' where it is hingedly secured by a pin 64 passing through the ends of the conduit E8, the ring 60 and the ell 62 to be peened over at 66. The other extremity of the ell 52 is similarly joined to a conduit 68 by a cross pin 19 and ring 12, the pin '18 being arranged in a plane substantially at right angles to the pin 64 so that the conduits 68 and 48 are joined universally by the ell 62 and rings 68, 12 with pins 54 and iii. The end of the conduit 65 joined to the ell is fixedly supported by a plate 1 secured to the hub ill by screw devices 15, and the opposite end of the conduit 68 joins with an annular channel member or ring 78 carried by the spinner supporting bulkhead 2B, which channel member is rotatively concentric with a similar annular channel or ring so supported by brackets 32 from the engine nosing or other rigid or fixed part.

The channel members i8, 80 are both concentrio with the axis of propeller rotation and together form a hot air manifold relatively rotatable for conducting hot air from a heater conduit 84 joining with the channel member Bi! after leaving a heating unit 85, such as an engine exhaust, and conducting air under pressure through a branch 88 from an air pressure pump 90. The pump is driven by any convenient gearing such as the spur 92 and is supplied with clean air through a supply line 94 from a filter unit 96. It is particularly desirable to clean and it may be desirable to dry the air that is to v be forced into the interior of the blade, so that there may be no corrosive effects or scaling of the metal. Therefore, the filter unit may incorporate a desiccator, but that is not generally feasible due to the volume of air being moved. Exhaust gases not being suitable, because of deleterious effects of the gases on the metal engaged, and due to the solid content carried by exhaust gases, the same are not used for heating the blade, but instead air at atmospheric pressure is taken in and cleaned by the filter 96, from where it is drawn into the pump 90 and placed under pressure to flow along the conduit 88 and around the heater 85 to be delivered through 8 to the fixed part 86 of the hot air manifold, where it is distributed by the rotating part 18 to the conduits 88, one for each blade,

relation as those for the leading edge.

faces 28 and St. Desirably, the hot air is kept flowing through the blade during its rotation, and thereby conditions the blade with such tem perature that ice will not form on its faces, or, if formed thereon will soon meltoif.

Further detailed construction of the blade M making it adaptable to the forced hot air heating is shown in Figs. '7 to 9, where the bulkhead 59 comprises a sheet metal cup-like member having peripheral flanges 93 and Hill bent out of the plane of the member and conforming to the contour of the members it is to engage in closing off the passage Q2. The flange is sub stantially cylindrical or arc-like to follow the outside contour of the spar shank [6, while the flange EEJE bounding the rest of the member follows the contour of the sheath for the leading edge and face portions. The flanges are so dimensioned that the member is will pass within the open end of the sheath loosely, and is packed by means of shims I02, Hill of phenolic material such as that known as Bakelite. The bulkhead and shims after assembly within the open end of the blade prevent chafing and are held in place by rivets or screw devices iilfi passing through the'end of the sheath, the shims and the flanges i536 of'the bulkhead. Similar devices lllii pass through the flange 28, the shank it of the spar and an angle bracket M0 to secure the bulkhead to the spar. The shims, aside from cushioning the union of the bulkhead in its support from the sheath and spar, also provide a substantial seal against the leakage of heated air from the hub end'of the blade chamber 42. I At the approximate central point'of the bulkhead fiii, there is provided a large aperture H2 for the passage of the conduit 43, by which the hot air is introduced to the blade chamber. The

gasket 52 hereinbefore mentioned is flanged to provide a sleeve portion embracing the conduit [18, and is so flexible as to yield and follow the wobble of the conduit as pitch shifting movement of the blade takes place. Distributed in triangular form around the aperture H2 there are a plurality of balance stations made up of studs lid secured in the body of the bulkhead 59 to extend outwardly from the chamber 42 and receive a selection of balance washers H6 held in place by a lock Washer H8 and nut I25. This arrangement adequately locates balance stations on the leading edge side of the spar to include 122 adjacent the leading edge, 524 on the pressure face side of the blade chord, and I26 on the camber face side of the chord. The bulkhead 56 is similarly constituted and mounted on the opposite side of the shank l6 and within the face portions of the sheath at the trailing edge of the blade, insofar as the flanges iZB, I30 and 132 with intervening gaskets or shims are secured in place by the screw devices I66 and IE8. This bulkhead is impervious to fluid movement but also provides a triangular arrangement of balance stations lSQ, 36 and H38 in about the same These balance stations :22, !2d, 125, I34, I33 and 138 function principally in balancing the blade in a vertical sense with respect to a master blade at the time of manufacture and are accessible for balancing in the field should occasion demand.

Contributing to the same end and for refining the balance with respect to other blades used on the same hub, there is a primary blade balancing unit H32 disposed axially of the spar and radially outward thereof to permit the mounting of a torque unit M2 by which pitch shifting of the blade is effected. This balance unit is principally for establishing horizontal balance, and embraces the angle brackets I!!! of the form shown in Figs. 7 and 8, in which a convex portion I44 fits against the inside of the shank I6 and ends with a ledge MB substantially at right angles to the axis of the spar 26, there being a medial web I 58 joining and bracing the portions I44 and I46. The convex portions I44 are apertured each side of the web I48 to receive the screw devices I08 attaching the flanges of the bulkheads to the spar, there being a shim I50 disposed between the angle bracket and the inside of the shank. On the radially outside of the ledge portion I 16 there are provided a pair of spaced safety nuts I52 accessible through aligned apertures of the ledge for reception of screw devices I54, by which a spanner or bridge member I56 is secured in position across the bore of the spar. The bridge I58 is of channel form in cross section to provide the stiffening ribs or flanges I58, and each-end of the bridge is slitted sufiiciently to straddle the proximate portion of the web I48. Each bifurcated end, so to speak, of the bridge member rests on the ledge portion I46 and is apertured to receive the screw devices Hi l by which the bridge is firmly secured to the ledges.

Extending transverse of the bridge I56 there is a rectangular cup member I66 that positions over locating dowels I62 and is held in place by screw devices I64. In each end of the cup'there is a partition I66 that provides a chamber I58 at each end of the cup which chamber is spanned by rivets or bars I it passing through the end wall of the cup and the partition I65 at some distance above the bottom of the cup. The bars Ilil' tend to prevent separation of the partitions from their respective end members of the cup and also provide an anchorage for retention of a body of balancing lead I '52 poured into the chamber of the cup while in the molten condition. It is customary to fix the cups Hid with the required or specified quantity of lead to accomplish approximate balance before the balance unit I M] is assembled within the blade shank. In this way the assembly of a blade by rote accomplishes all but a trimming balance effected by adding shims or washers H 3 beneath a nut I16 and washer I18 mounted on a rigid stud I 8i secured in the center of the bridge I56, and extending through the bottom of the cup I63.

The assembly of the bulkheads and balance unit within the blade is accomplished after the manner of connecting sub-assemblies. That is, with the blade otherwise complete, the bulkheads 58 and 56, which have theretofore been assembled with their balance stations, are inserted and retained in place by means of the screw devices N36. The angle brackets IIQ with the shims I55 are then positioned within the bore of the strut and secured in place by the screw devices I98 which also secure the flanges 93 and I 28 with their respective shims in firm support to the shank I5. All of the screw devices I06 and I93 may now be tightened as desired. The remainder of the balance unit is assembled piece by piece upon the angle brackets I I9, because of the accessibility through the clearance I 82 of the hollow shank it. The bridge piece I56 is passed through the opening I 82 and tilted to engage on the ledges I l-6 01 brackets, after which the screw devices I54 are threaded into place in the safety nuts I52 secured to the opposite side of the ledges. Next, the lead bearing cup lfiil is passed through theopening I82 and tilted to occupy a position extending across the bridge member I56 and is then passed over the stud I89 so as to position over the dowels I52 which allows insertion of screw devices te l that thread into safety nuts I65 secured to the channel side of the bridge member I56. In so mounting the lead charged cup IE8, it is usual to insert an appropriate shim I3 1 between the cup and the engaged surface of the bridge piece I56. With tightening of the screw devices and mounting the required number of washers I Hi, the con struction and assembly of the blade is complete, and it is now ready for assembly within a socket i 2 of the propeller hub, such as to be disposed over the torque unit I42. The torque unit is usually fixed to a blade shifting gear 885 comprising part of the hub assembly, and affording driving dowels for one way engagement with the end of the blade. Hence, after the assembled blade is passed over the torque unit, which is possible because of the clearance between the torque unit and the opening E82 of the blade shank, the blade is retained in its pitch shifting relation by the usual stack bearings carrying the thrust from a blade nut I 88 backed up by a blade retaining nut I99 threaded into the outer end of the socket i2, and well known to those experienced in the art, being completely shown and described in the patent to Blanchard et al. 2,307,101. Such a construction is illustrated in Fig. l of the drawings, where the space between the radially inward end of the blade I4 and the surface of the spinner I?! may be closed by a skirt E92 clamped or otherwise secured. to the end of the blade as at I94. The entire structure is thereby faired; and the conduit 58 is enclosed within the skirt I32 whereby undue cooling of the hot air within is prevented. Yet the blades are permitted to turn in their pitch shifting movement due to the clearance I95 between the skirt and spinner.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. In a controllable pitch aircraft propeller having hollow blades with a bulkhead at the radially inward end thereof, a heating system for heating the sheath of each blade, comprising articulated rigid fluid conduit means, one end of which extends through the bulkhead of the blade and the other end of which is fixed relative to the propeller hub assembly, a hot air pressure line ending in a manifold with which the fixed end of the conduit communicates, and means for cleaning the atmospheric air entering the pressure line.

2. The combination set forth in claim 1 in which the first mentioned end of the conduit is universally joined to the second mentioned end of the conduit and is capable of oscillation with the blade as it rotates on its axis in pitch shifting movement.

3. The combination set forth in claim 1 in which the said manifold comprises a pair of concentric telescoping rings, one of which is mounted on the propeller hub, and the other of which is rigidly supported to be rotatable relative to the first.

4. The combination set forth in claim 1 wherein the conduit means for conducting the hot air comprises rigid conduit sections universally joined together and rigidly secured at one end 7 length thereof and bonded together to provide a pair of lineally extending chambers, and bulkheads closing off the radially inward end of the chambers, and wherein the air conducting means comprises a conduit section universally mounted on the propeller and extending through the bulkheadfor the leading edge side of the blade.

6. In an aircraft propeller provided with ice removing means, a hollow blade adapted to be mounted in a hub and capable of pitch shifting movement, comprising in combination, a hollow spar closed at the tip end, a sheet metal sheath mounted on the spar and extending beyond the end of the spar to form a pair of chambers on each side of the spar and connected at their tip ends, bulkheads fitted to the spar at the radially inward end of the sheath to close off the chambers, an opening provided by one of the bulkheads for admission of heated air, an opening provided at the tip end of the blade exhausting from the radially outward end of the other chamber whereby hot air entering through the bulkhead traverses the length of the blade and across the tip of the blade to exit at the retreating edge of the blade.

7. In anti-icing means for variable pitch propellers having hollow blades, the combination comprising, a fixed manifold member, a cooperating manifold member carried by the propeller and continuously in fluid communication with the fixed manifold member, conduit means leading from the cooperating manifold member to the hollow blade and including a rigid tubular element fixedly supported by the propeller, a movable tubular element extending into the blade and supported for oscillation due to blade shift movement, and means articulating the movable tubular element and the rigid tubular element so that the flow of fiuid medium through the conduit means is not interrupted at any oscillated position of the movable tubular element.

8. In anti-icing of hollow propeller blades mounted for pitch shifting movement upon a propeller hub, the combination comprising, an annular manifold member supported by the hub to which hot air is conducted, rigid conduit means external, of the hub for conducting hot air from the manifold member to the blade comprising, a tubular section supported rigidly by the hub and extending from the manifold member, a second tubular section universally supported by the hub and extending into the hollow blade, joint means firmly supported by the hub and connecting the hub supported ends of both tubular sections so that the fluid passage through the tubular sections is not interrupted at any position of the blade with respect to the hub.

JOSEPH STUART, III. WARREN D. BERKLEY.

REFERENCES CITED The following references are of record in the file of this patent:

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